About 40 years ago, the first major technological conversion in oilwell drilling took place when the industry abandoned steam rigs and adopted power rigs. During the ten years preceeding 1935, when I drilled my last well with a steam powered rig, I could see that steam rotary rigs were becoming obsolete. Anywhere from ten days to three weeks of preparation were required to start drilling with a medium sized rig, capable of drilling in the range of 5000 feet to 8000 feet. Installation required setting up a wooden or steel derrick, three to five boilers, fuel tanks, a water treatment system, and steam pressure pipe lines all contributing to a very inefficient source of power.
The changeover to power rigs resulted in a more efficient, simplified system. Usually all that was required was to arrange engine compounds, chain or gear transmissions, fluid couplings torque converters and air operated friction clutches. Increased portability of rigs was a significant development, particularly in shortening set up time, as evidenced by twenty or more of my own patents issued over the last thirty or more years. Specifically, with some of my rigs it is possible to move, set up and spud a well in as short a time as 8 hours.
Although set up times have been considerably shortened, the mechanical disadvantages of power rigs remain. An average rig has miles of line, up to eight or ten friction clutches, hundreds of bearings and enclosed chain gear cases and elaborate hydromatic or electro-magnetic braking systems, as well as drawworks, sprockets, drums, line spoolers and travelling blocks. Little has been done to improve drilling rigs since the late 1950's, since few rigs have been manufactured and sold. Manufacturers' attention has been devoted to offshore drilling and most manufacturers have order backlogs of up to ten years to fulfill.
In the past 10 to 15 years, hydraulic systems have virtually totally replaced mechanical components in equipment such as fork lifts, cranes, bulldozers, graders, skip loaders and similar items. Little has been done in the oilwell drilling industry where progress has been very slow.
One early example of a hydraulic drilling rig was on display at the Tulsa International Oil Show, Tulsa, Oklahoma, in 1948. Unfortunately the design was poor and the unit finally wound up at a scrap yard in Long Beach, California.
Resistance of the industry to apply hydraulics to oil well drillings is well evidenced by the paucity of available patent literature on the subject, other than my own patents and a few others disclosing hydraulics used in oil well pumps. U.S. Pat. No. 2,807,441 issued to B. W. Sewell on Sept. 24, 1975, discloses a very small, portable hydraulic drilling rig with a single cylinder 14 while U.S. Pat. No. 2,438,277 issued to R. E. Fife et al on Mar. 23, 1948 shows hydraulics used with the mast of a service rig. A hydraulically actuated cat line is disclosed in U.S. Pat. No. 2,324,096 issued to R. M. Lilley on July 13, 1943. Basic hydraulics for a remote environment lift are illustrated in U.S. Pat. No. 2,897,907 issued to A. E. Blount on Aug. 4, 1959.
More significant and basic developments in the application of hydraulics to oilwell drilling servicing and/or pumping are found in my own prior U.S. Pat. Nos. 3,345,950, issued Oct. 10, 1967; 3,538,777, issued Nov. 10, 1970; 3,777,491 issued Dec. 11, 1973; and 3,792,836, issued Feb. 19, 1974.
This last mentioned patent discloses my first major development of a completely hydraulic well rig but does not disclose major improvements as disclosed herein, including a more sophisticated and reliable power source and an improved safety dump valve assembly. The fluid pressure operated differential piston safety dump valve as disclosed herein eliminates the need for sophisticated internal construction of the piston cylinder fluid motors, such as disclosed in my prior U.S. Pat. No. 3,792,836, and is far more reliable than the simple check valve 77 disclosed in U.S. Pat. No. 2,897,907 discussed above. Other remote environment differential piston valves are disclosed in prior U.S. Pat. Nos. 1,112,109 issued Sept. 29, 1914 to J. Billingham et al; 3,244,396 issued Apr. 5, 1966 to A. L. Miller; 3,519,022 issued July 7, 1970 to K. Chung et al; 3,542,332 issued Nov. 24, 1970 to A. A. Chevalier et al; and 3,734,455, issued May 22, 1973 to P. J. Natho et al.